In general, a steering column of a vehicle is a mechanical component that transmits a steering force applied to a steering wheel to wheels. The structure of the steering column is shown in FIG. 1. That is, a steering wheel 1a is fixed to a steering column 1, and a pinion shaft 3a is provided in a steering gearbox 3 that performs a steering operation, using the rotation caused by the movement of a rack bar during the steering. The steering column is connected with the pinion shaft by a shaft 50.
In this case, a shaft 50 passes through a dashboard 5, and the dashboard 5 is provided with a dust cover 52 shown in FIG. 2 in order to intercept noise and foreign substances transmitted into a vehicle cabin from an engine room. Further, an oilless bearing 54 shown in FIG. 3 is fitted into an inner portion of the dust cover 52, and the shaft 50 is inserted into the oilless bearing 54.
Furthermore, as shown in FIG. 4, the shaft 50 includes a protruding portion such as a convolute tube 50a that protrudes toward the outside of the shaft 50 so as to allow the shaft 50 to contract in an axial direction during the collision of a vehicle. A plurality of grooves 54a is formed on inner circumferential surface of the oilless bearing 54 so as to be complementarily engaged with the protrusions of convolute tube 50a. 
Meanwhile, the shaft 50 should be moved in an axial direction (indicated by an arrow in FIG. 4) from the engine room toward the vehicle cabin in order not to interfere with an engine module during the mounting of an engine module. For this purpose, tolerance should be formed between the shaft 50 and the oilless bearing 54 so as to allow the convolute tube 50a to be moved. That is, the tolerance is formed between the convolute tube 50a of shaft 50 and the grooves 54a of oilless bearing 54.
As a result, a clearance is formed between the shaft 50 and the oilless bearing 54 so as to allow the convolute tube 50a to be moved with respect to the grooves 54a. 
However, the clearance has an undesirable effect such as interception of noise and foreign substances transmitted from the engine room to the vehicle cabin.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.